JP2020045516A - Method for smelting oxide ore - Google Patents

Abstract

To provide a method for smelting an oxide ore capable of efficiently recovering a metal contained in the oxide ore.SOLUTION: A method for smelting an oxide ore comprises: a reduction step of charging a mixture of the oxide ore and a carbonaceous reducing agent into a reduction furnace to subject the mixture to a heating reduction treatment; a quenching step of quenching the resulting reduced product immediately after taking out the reduced product from the reduction furnace; and a separation step of separating a metal and slag from the reduced product after quenching. In the quenching step, the resulting reduced product is put into water to quench, for example.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for smelting an oxide ore, for example, a method for smelting an oxide ore such as a nickel oxide ore as a raw material with a carbonaceous reducing agent to obtain a reduced product.

  As a method for smelting nickel oxide ore called limonite or saprolite, which is a kind of oxide ore, a dry smelting method that uses a smelting furnace to produce nickel matte, and iron and nickel using a rotary kiln or a moving hearth furnace Smelting method (hereinafter referred to as “ferronickel” as an alloy of iron and nickel), acid leaching at high temperature and pressure using an autoclave, and mixed sulfide (mixed sulfide) mixed with nickel and cobalt ) Is known.

  Among the various methods described above, particularly when reducing and smelting nickel oxide ore using a dry smelting method, the nickel oxide ore as a raw material is crushed to an appropriate size in order to advance the reaction. Agglomeration processing is performed as preprocessing.

  Specifically, when the nickel oxide ore is agglomerated, that is, when the powdered or fine ore is agglomerated, the nickel oxide ore is mixed with other components, for example, a reducing agent such as a binder or coke. The mixture is then adjusted for water content, and then charged into a lump manufacturing machine, for example, a molded product (pellet, briquette, or the like having a side or diameter of about 10 mm or more and 30 mm or less; hereinafter, simply referred to as “pellet”. It is common to say).

  The pellets obtained by agglomeration need to have a certain degree of air permeability in order to "blow off" the contained water. Further, if the reduction does not proceed uniformly in the pellets in the subsequent reduction treatment, the composition of the obtained reduced product becomes non-uniform, which causes inconveniences such as dispersion or uneven distribution of the metal. Therefore, it is important to uniformly mix the mixture when preparing pellets and to maintain the temperature as uniform as possible when reducing the obtained pellets.

  In addition, it is a very important technique to coarsen the metal (ferronickel) generated by the reduction treatment. When the produced ferronickel has a fine size of, for example, several tens μm or more and several hundreds μm or less, it is difficult to separate the slag from the slag produced at the same time, and the recovery rate (yield) as ferronickel is greatly reduced. I will. Therefore, a treatment for coarsening the reduced ferronickel is required.

  For example, in Patent Document 1, an agglomerate containing a metal oxide and a carbonaceous reducing agent is supplied onto a hearth of a moving bed type reduction melting furnace and heated to reduce and melt the metal oxide. In the manufacturing method, the relative value of the projected area ratio of the agglomerate to the hearth with respect to the maximum projected area ratio of the agglomerate to the hearth when the distance between the agglomerates is 0 is defined as the floor density. A method is disclosed in which agglomerates having an average diameter of 19.5 mm or more and 32 mm or less are supplied onto a hearth so as to have a bed density of 0.5 or more and 0.8 or less, and are heated. In this method, it is described that the productivity of granular metallic iron can be increased by controlling the bed density and the average diameter of the agglomerate together.

  However, in the method using a material having a specific diameter as an agglomerate as disclosed in Patent Document 1, it is necessary to remove an agglomerate having no specific diameter. It was low. In addition, the method disclosed in Patent Literature 1 requires that the bed density of the agglomerate be adjusted to 0.5 or more and 0.8 or less, and the agglomerate cannot be laminated. Was. For these reasons, the method disclosed in Patent Document 1 has a high manufacturing cost.

  As described above, the technology of producing a metal or an alloy by mixing and reducing an oxide ore has many problems in terms of increasing productivity, reducing production cost, and improving metal quality.

JP 2011-256414 A

  The present invention provides a smelting method for producing a metal by reducing a mixture containing an oxide ore such as a nickel oxide ore, which can improve the quality of the obtained metal and efficiently produce a high-quality metal. It is an object of the present invention to provide a method for smelting an oxide ore that can be performed.

  The present inventor has found that the above problem can be solved by quenching immediately after the heat-reduced reduced product has been taken out of the reduction furnace, and has completed the present invention.

  (1) A first step of the present invention is a reduction step of charging a mixture containing an oxide ore and a carbonaceous reducing agent into a reduction furnace and performing a heat reduction treatment, and taking out the obtained reduced product from the reduction furnace. A smelting method of an oxide ore including a quenching step of immediately cooling the reduced product and a separation step of separating metal and slag from the quenched reduced product.

  (2) A second aspect of the present invention is the method for refining an oxide ore according to the first aspect, wherein the obtained reduced product is put into water and quenched in the quenching step.

  (3) A third aspect of the present invention is the method for smelting oxide ore in the first or second aspect, wherein the reducing step is performed by reducing the reduction temperature to 1200 ° C or higher and 1450 ° C or lower.

  (4) In a fourth aspect of the present invention, in any one of the first to third aspects, in the reduction step, after the heat reduction treatment, the obtained reduced product is maintained at a predetermined temperature in the reduction furnace. This is a method for smelting oxidized ore.

  (5) A fifth aspect of the present invention is the method for refining an oxide ore in which the oxide ore is a nickel oxide ore according to any one of the first to fourth inventions.

  ADVANTAGE OF THE INVENTION According to the smelting method of the oxide ore which concerns on this invention, a high quality metal can be manufactured efficiently.

It is a flowchart showing an example of a flow of a smelting method of nickel oxide ore.

  Hereinafter, specific embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and various changes can be made without changing the gist of the present invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

≪1. Outline of smelting method of oxide ore
In the method for smelting oxide ore according to the present embodiment, oxide ore (oxide) as a raw material ore is mixed with a carbonaceous reducing agent, and the mixture (pellet) is mixed in a smelting furnace (reduction furnace). By performing the reduction treatment, metal and slag are generated.

  For example, as an oxide ore, a nickel oxide ore containing nickel oxide or iron oxide is used as a raw material, the nickel oxide ore is mixed with a carbonaceous reducing agent to form a mixture, and nickel contained in the mixture is prioritized. And a method of producing ferronickel, which is an alloy of iron and nickel, by reducing iron and partially reducing iron.

  And in the smelting method of the oxide ore according to the present embodiment, the obtained reduced product is taken out from the reduction furnace, and immediately thereafter, the reduced product is quenched, and the metal and slag are separated from the quenched reduced product. It is characterized by:

  According to such a method, since the reductant in the heated state is rapidly cooled immediately after being taken out of the reduction furnace, it is possible to suppress the oxidation of the reductant due to the heat of the heat reduction treatment. Thereby, the quality of the obtained metal can be improved.

{2. Smelting method for producing ferronickel using nickel oxide ore.
In the following, nickel (nickel oxide) and iron (iron oxide) contained in the nickel oxide ore, which is the raw material ore, are reduced to produce a metal of an iron-nickel alloy, and the ferromagnetic material is separated by separating the metal. A smelting method for producing nickel will be described as an example.

  Specifically, as shown in FIG. 1, the smelting method of nickel oxide ore according to the present embodiment includes a mixing step S1 of mixing nickel oxide ore and a carbonaceous reducing agent to obtain a mixture, and reducing the mixture. A reducing step S2 for charging the furnace and subjecting it to a heat reduction treatment, a quenching step S3 for taking out the obtained reduced product from the reducing furnace and immediately quenching the reduced material, And a separation step S4 for separation.

<2-1. Mixing process>
The mixing step S1 is a step of mixing a nickel oxide ore and a carbonaceous reducing agent to obtain a mixture. Specifically, first, a carbonaceous reducing agent is added to and mixed with nickel oxide ore as a raw material ore, and iron ore, a flux component, a binder and the like having an optional particle size of, for example, 0%. A powder of about 0.2 mm or more and 0.8 mm or less is added and mixed to obtain a mixture. Note that the mixing process can be performed using a mixer or the like.

The nickel oxide ore, which is a raw material ore, is not particularly limited, and limonite ore, saprolite ore, or the like can be used. Note that the nickel oxide ore contains at least nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ).

  Although it does not specifically limit as a carbonaceous reducing agent, For example, coal powder, coke powder, etc. are mentioned. It is preferable that the carbonaceous reducing agent has a particle size and a particle size distribution equal to those of the nickel oxide ore, which is a raw material ore, because it is easy to mix uniformly and the reduction reaction easily proceeds uniformly.

  As the content of the carbonaceous reducing agent (the content of the carbonaceous reducing agent contained in the mixture), the chemical equivalent required to reduce the total amount of nickel oxide constituting the nickel oxide ore to nickel metal and the iron oxide ( When the total value of the chemical equivalents required to reduce ferric oxide to metallic iron (also referred to as the “sum of the chemical equivalents” for convenience) is 100% by mass, 50% by mass or less. The ratio is preferably set to 40% by mass or less, and more preferably set to 40% by mass or less. The amount of iron reduction can be suppressed, the nickel quality can be increased, and high quality ferronickel can be manufactured.

  The mixing amount of the carbonaceous reducing agent is preferably 10% by mass or more, more preferably 15% by mass or more, when the total value of the chemical equivalents is 100% by mass. The reduction of nickel can proceed efficiently and productivity can be improved.

  As the iron ore as an optional additive, for example, iron ore having an iron grade of about 50% by mass or more, hematite obtained by hydrometallurgy of nickel oxide ore, or the like can be used.

  Examples of the flux component include calcium oxide, calcium hydroxide, calcium carbonate, and silicon dioxide. Examples of the binder include bentonite, polysaccharide, resin, water glass, dehydrated cake, and the like.

  In the mixing step S1, a mixture is obtained by uniformly mixing raw material powders containing nickel oxide ore. Table 1 below shows an example of the composition (% by mass) of some of the raw material powders mixed in the mixing step S1, but the composition of the raw material powders is not limited to this.

  At the time of this mixing, kneading may be performed at the same time to enhance the mixing property, or kneading may be performed after the mixing. The kneading can be performed using a batch type kneader such as Brabender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a single-screw kneader, a twin-screw kneader, or the like. By kneading the mixture, a shear force is applied to the mixture to disperse the agglomeration of the carbonaceous reducing agent, raw material powder, etc., thereby enabling uniform mixing, improving the adhesion of each particle, and reducing voids. Can be. As a result, the reduction reaction easily occurs in the mixture, and the mixture can be uniformly reacted, and the reaction time of the reduction reaction can be shortened. Further, variation in quality can be suppressed.

  After mixing, or after mixing and kneading, the mixture may be extruded using an extruder. As a result, a pressure (shearing force) is applied to the mixture, and the aggregation of the carbonaceous reducing agent, the raw material powder, and the like is released, and the mixture can be more uniformly mixed. Furthermore, voids in the mixture can be reduced. From these facts, the reduction reaction of the mixture tends to occur uniformly in the reduction step S2 described later, the quality of the obtained metal can be improved, and a high-quality metal can be manufactured.

  The extruder is preferably one capable of kneading and molding the mixture under high pressure and high shear force, and examples thereof include a single screw extruder and a twin screw extruder. In particular, it is preferable to provide a twin-screw extruder. By kneading the mixture at a high pressure and a high shear, the aggregation of the mixture of the raw material powders can be broken, the kneading can be effectively performed, and the strength of the mixture can be increased. In addition, by using a twin-screw extruder, a mixture can be obtained while maintaining high productivity continuously.

  Further, the mixture may be formed into a molded product (pellet) having a predetermined shape. The shape of the molded product can be, for example, spherical, rectangular, cubic, cylindrical, or the like. Since such a shape is a simple shape and not complicated, it is possible to suppress the occurrence of defective products while suppressing the molding cost, the quality of the obtained molded product is also uniform, and the reduction in yield is suppressed. can do.

  The shape of the molded product is particularly preferably spherical. By being a spherical molded product, the reduction treatment can be performed uniformly, and smelting with little variation and high productivity can be performed. When the shape of the molded product is spherical, it can be molded so that the diameter is about 10 mm or more and about 30 mm or less. In the case of a rectangular parallelepiped shape, a cubic shape, a columnar shape, or the like, it can be formed so that the vertical and horizontal inner dimensions are approximately 500 mm or less.

The size of the molded product is not particularly limited, but the volume of the molded product is preferably 8000 mm ³ or more. When the volume of the molded product is 8000 mm ³ or more, the molding cost is suppressed, and the ratio of the surface area to the entire molded product is reduced. Therefore, the heat reduction treatment is uniformly performed, the variation is small, and the productivity is low. High smelting can be performed.

  Further, the obtained molded product may be filled in a predetermined container for reduction. By performing the reduction treatment in a state where the molded product filled in the container is filled in the container, the metal reduced in the separation step S4 to be described later can be easily separated and collected by a process such as magnetic separation. Can be suppressed.

  The method for filling the reduction container with the molded product can be performed by sequentially supplying the molded product to the container using an extruder or the like. The container for reduction is not particularly limited, but a container having a rectangular parallelepiped or a cubic shape can be used. The size of the container is also not particularly limited, but, for example, in the case of a rectangular parallelepiped shape, when viewed from the top surface, the vertical and horizontal inner dimensions of the surface are 50 mm or more and 1000 mm or less, and the internal height is 5 mm or more and 500 mm or more. It is preferable to use the following. The container for reduction is not particularly limited, but may be made of a material that does not cause adverse effects at the time of the reduction treatment on the molded product filled in the container and that allows the reduction reaction to proceed efficiently. preferable. Specifically, a crucible made of graphite, a material made of ceramic or metal, or the like can be used.

  In the mixing step S1, the obtained mixture may be subjected to a drying treatment. The mixture is mixed with a large amount of water in kneading or molding of a molded product. Although it is not an essential aspect to perform the drying treatment in the present embodiment, by performing the drying treatment on the mixture containing a large amount of water, it is possible to prevent the expansion of the mixture due to the vaporization of moisture in the reduction treatment described below. .

  The method for drying the mixture is not particularly limited, for example, a method of maintaining the mixture at a predetermined drying temperature (for example, 300 ° C. or more and 400 ° C. or less), a method of blowing hot air at a predetermined drying temperature against the mixture, and drying. Conventionally known means can be used. By such a drying treatment, for example, the solid content of the mixture is about 70% by mass and the water content is about 30% by mass. Note that the temperature of the mixture itself during the drying treatment is preferably less than 100 ° C., because bursting of the mixture due to bumping of water from the inside of the mixture or the like can be suppressed.

  Further, the drying treatment may be continuously performed at once or may be performed in a plurality of times. Burst of the mixture can be more effectively suppressed by performing the drying treatment in a plurality of times. In the case where the drying treatment is performed a plurality of times, the second and subsequent drying temperatures are preferably 150 ° C. or more and 400 ° C. or less. By drying in this range, drying can be performed without the reduction reaction proceeding.

  Table 2 below shows an example of the composition (parts by mass) in the solid content of the mixture after the drying treatment. The composition of the molded product is not limited to this.

（※固形分の組成において、上記以外の成分は残部である。）

(* In the composition of solid content, components other than the above are the balance.)

<2-2. Reduction process>
The reduction step S2 is a step of charging the obtained mixture into a reduction furnace and performing a heat reduction treatment at a predetermined reduction temperature. By the heat reduction treatment in the reduction step S2, a smelting reaction (reduction reaction) proceeds, and ferronickel metal (hereinafter, simply referred to as “metal”) and ferronickel slag (hereinafter, simply referred to as “slag”) are separated. Generate.

  Specifically, the heat reduction treatment in the reduction step S2 is performed by charging a mixture containing nickel oxide ore into a reduction furnace heated to a predetermined reduction temperature. In the heat reduction treatment, the nickel oxide contained in the nickel oxide ore, which is the raw material ore, is reduced as completely and preferentially as possible, while the iron oxide contained in the nickel oxide ore is partially reduced. The so-called partial reduction is performed to obtain the desired high nickel grade ferronickel.

  In the heat reduction treatment, nickel oxide ore and iron oxide in the mixture are reduced and metallized to ferronickel in the vicinity of the surface of the mixture in which the reduction reaction is likely to proceed, for example, in a short time of about 1 minute. To form On the other hand, in the shell, the slag component is gradually melted with the formation of the shell, and slag in a liquid phase is generated. Thereby, the metal and the slag are separately generated in the mixture.

  Then, when the treatment time elapses about 10 minutes, the excess carbonaceous reducing agent not involved in the reduction reaction is taken into the metal to lower the melting point, so that the metal also becomes a liquid phase. In addition, the volume of this reduced product has shrunk to about 50% or more and 60% or less as compared with the mixture charged in the reduction furnace.

  The temperature (reduction temperature) in the heat reduction treatment is not particularly limited, but is preferably in the range of 1200 ° C to 1450 ° C, more preferably in the range of 1300 ° C to 1400 ° C. By performing reduction in such a temperature range, a reduction reaction can be uniformly generated, and ferronickel with reduced quality variation can be generated. More preferably, by performing the reduction at a reduction temperature in the range of 1300 ° C. or more and 1400 ° C. or less, a desired reduction reaction can be caused in a relatively short time.

  The time (treatment time) in the heat reduction treatment is set according to the temperature of the reduction furnace, but is preferably 10 minutes or more, and more preferably 15 minutes or more.

  In the heat reduction treatment, the internal temperature of the reduction furnace may be increased by, for example, a burner until the reduction temperature in the above-described range is reached, and the temperature may be maintained after the temperature increase.

  In addition, it is preferable that the calorie required for the reduction by multiplying the value of the reduction temperature (° C.) by the numerical value of the reduction time (min) is in the range of 20,000 (° C. × min) to 40,000 (° C. × min) or less. Thereby, a high quality metal can be efficiently manufactured.

  The reduction furnace is not particularly limited. A single furnace may be used, or a furnace such as a moving hearth furnace which can be continuously processed in each process by rotating a hearth or the like may be used. Among them, by using a moving hearth furnace as the reduction furnace, the reduction reaction can proceed continuously and the reaction can be completed with one facility. In addition, when the operation is performed using a separate furnace for each process, there is a possibility that a heat loss may occur due to a decrease in temperature when moving between furnaces. Further, a change may occur in the atmospheric gas, and it may not be possible to immediately cause a reaction when the gas is recharged into the furnace. In this regard, using a moving hearth furnace to perform each process in a single facility reduces heat loss and enables accurate control of the furnace atmosphere, allowing the reaction to proceed more effectively. Can be.

  The moving hearth furnace is not particularly limited. For example, a rotary hearth furnace having a circular shape and divided into a plurality of processing regions can be used. In a rotary hearth furnace, each process is performed in each region while rotating in a predetermined direction. In this rotary hearth furnace, the processing temperature in each area can be adjusted by controlling the time (moving time, rotation time) when passing through each area, and the rotary hearth furnace makes one rotation. Each time the mixture is smelted. The moving hearth furnace may be a roller hearth kiln or the like.

  In the heat reduction treatment, before charging the mixture obtained from the mixing step S1 into the reduction furnace, a carbonaceous reducing agent (hereinafter, also referred to as “hearth carbonaceous reducing agent”) is previously added to the hearth in the reduction furnace. The mixture may be laid and the mixture placed on the laid hearth carbonaceous reducing agent. Alternatively, a floor covering material mainly composed of an oxide may be laid on the hearth, and the mixture may be placed thereon. In this way, the reaction between the hearth and the mixture can be suppressed by laying the carbonaceous reducing agent, the floor covering material, etc. on the hearth and placing the mixture on the carbonaceous reducing agent, thereby extending the hearth. Life can be extended.

  Here, after the above-described heat reduction treatment, a temperature holding treatment may be performed to hold the obtained reduced product composed of metal and slag at a predetermined temperature in the same reduction furnace. More specifically, in the temperature holding process, the reduced product obtained by the heat reduction process is held in the same reduction furnace at a predetermined temperature for a certain period of time without being taken out of the reduction furnace.

  As described above, by performing the temperature holding treatment on the reduced product in the same reduction furnace, the metal can be effectively settled in the reduced product in the semi-molten state to promote the separation of the metal phase and the slag phase. it can. As a result, the metal recovery rate can be increased, and higher quality metal can be obtained.

  The atmosphere gas in the reduction furnace after the heat reduction treatment is mainly a CO gas derived from a carbonaceous reducing agent, which contains a large amount of a reducing gas such as CO and also includes an inert gas. Oxidizing gas such as Therefore, in the reduction furnace after the heat-reduction treatment containing almost no oxidizing gas such as oxygen, the obtained reduced product is subjected to a predetermined condition in a state accompanied by the atmospheric gas (the reduced product is cut off from the oxidizing atmosphere). By maintaining the temperature at the temperature, it is possible to precipitate the metal in the reduced product while effectively suppressing the oxidation of the metal in the reduced product.

  The processing time (temperature holding time) of the temperature holding processing is not particularly limited, but is preferably 10 minutes or more and 1000 minutes or less, and more preferably 30 minutes or more and 180 minutes or less.

<2-3. Rapid cooling process>
The quenching step S3 is a step of taking out the obtained reduced product from the reduction furnace and quenching the reduced product immediately after the removal. Specifically, immediately after the reduced product is taken out of the reduction furnace, the heated reduced product is rapidly cooled.

  When the reduced product obtained by the heat reduction treatment is taken out of the reduction furnace into the atmosphere, the reduced product is exposed to an oxidizing atmosphere, and the metal is oxidized. In addition, since the reduced product is in a state of receiving high-temperature heat until it is cooled, it is in a state where oxidation of metal is further promoted by contact with the atmosphere. When the metal obtained by the heat reduction treatment is oxidized, the quality of the metal is reduced.

  Therefore, the present embodiment is characterized in that immediately after the reduced product is taken out of the reduction furnace, the reduced product is rapidly cooled. As a result, it is possible to reduce the cooling time of the reduced product, and it is possible to suppress the metal from being oxidized due to the contact of the reduced product in a heated state with the atmosphere. The quality of metal can be improved.

  In addition, since the metal and slag contained in the reduced product have different heat shrinkage rates, by rapidly cooling the reduced product, cracks can be generated at the interface between the heat-shrinked metal and the slag, or Since the metal itself can be split naturally, the metal and the slag can be easily separated in the separation step S4 described below.

  The method for rapidly cooling the reduced product is not particularly limited, and examples thereof include a method in which the reduced product is brought into contact with a cooling medium and cooled. In this case, the cooling medium is not particularly limited as long as it can effectively quench the reduced product. For example, a liquid such as water or liquid nitrogen, or a solid such as ice or dry ice can be used. When the reduced product is brought into contact with the cooling medium, the amount of the cooling medium is not particularly limited, but is preferably such an amount that all the cooling medium does not evaporate.

  For example, water can be used as a cooling medium for cooling the reduced product. Specifically, the reduced product taken out of the reduction furnace is cooled by being poured into water stored in a cooling tank or the like. Such a method is preferable because it is simple and can effectively cool the reduced product. In addition, when the reduced product is put into water, it is preferable to circulate the water or replenish the water in order to more efficiently release heat and cool the reduced product.

  In rapidly cooling the reduced product, the cooling rate is preferably 50 ° C./min or more, and more preferably 70 ° C./min or more, depending on the temperature of the reduced product immediately after being taken out of the reduction furnace. More preferably, the cooling rate is 120 ° C./min or more. When the cooling rate is 50 ° C./min or more, the cooling time of the reduced product can be shortened, and the oxidation of the metal contained in the reduced product can be more effectively suppressed. The upper limit of the cooling rate is not particularly limited, but is preferably such a rate that the cooling medium is not instantaneously vaporized in a large amount.

<2-4. Separation process>
The separation step S4 is a step of separating metal and slag from the obtained reduced product. Specifically, the metal phase is separated and recovered from a mixture (reduced product) containing a metal phase (metal solid phase) and a slag phase (slag solid phase) obtained by reduction heating treatment of the mixture.

  As a method of separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid, for example, in addition to removing unnecessary substances by sieving, separation by specific gravity, separation by magnetic force, and the like Method can be used.

  In addition, the obtained metal phase and slag phase can be easily separated because of poor wettability, and for large inclusions, for example, a predetermined head is provided for dropping, or when sieving. By giving an impact such as giving a predetermined vibration, the metal phase and the slag phase can be easily separated from the mixture.

  In particular, in the present embodiment, since the reductant immediately after being taken out of the reduction furnace is quenched in the above-mentioned quenching step S3, cracks are intentionally generated at the interface between the metal and the slag due to the thermal contraction caused by the quenching. Can be generated, the pulverization of the reduced product can be facilitated, and the metal phase and the slag phase can be separated more efficiently.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

<Examples and comparative examples>
Nickel oxide ore, iron ore, silica or sand and limestone as flux components, binder, and carbonaceous reducing agent (coal powder, carbon content: 85% by mass, average particle size: about 180 μm) as raw material ores in appropriate amounts While adding water, mixing was performed using a mixer to obtain a mixture. The amount of the carbonaceous reducing agent (coal powder) required to reduce nickel oxide and iron oxide (Fe ₂ O ₃ ) contained in the nickel ore, which is the raw material ore, is 100 mass%. Was contained in an amount of 25% by mass according to the mixture. Table 3 below shows the mixture solids composition (excluding carbon) after the drying treatment. Then, the obtained mixture was equally divided into 12 samples.

Next, a hearth protecting agent (main component is SiO ₂ and a small amount of oxides such as Al ₂ O ₃ and MgO as other components) is provided in the hearth of the reduction furnace in a nitrogen atmosphere containing no oxygen. And 12 mixtures (samples) were placed thereon. The temperature condition during charging was 500 ± 20 ° C.

  Then, the temperature of the reduction furnace is raised until the temperature (reduction temperature) of the portion where the temperature becomes highest among the surfaces of the mixture charged in the furnace reaches the temperature shown in Table 4 below, and the mixture is heated and reduced. Processing was performed. The treatment time of the heat reduction treatment was set to the time shown in Table 4 below.

  After the heat reduction treatment, the samples of Examples 1 to 7 were put into a large amount of water immediately after being taken out of the reduction furnace to rapidly cool the samples. On the other hand, the samples of Comparative Examples 1 to 5 were taken out of the reduction furnace and then allowed to cool to room temperature in the atmosphere.

  After cooling, each of the samples of Examples 1 to 7 and Comparative Examples 1 to 5 was pulverized under the same conditions using a pulverizer, and then the metal was recovered by magnetic separation under the same conditions using a magnetic separator.

  For each sample after the reduction heat treatment, the nickel metallization ratio and the nickel content in the metal were analyzed and calculated using an ICP emission spectrometer (SHIMAZU S-8100).

The nickel metalization ratio and the nickel content in the metal were calculated by the following equations (1) and (2).
Nickel metallization rate = mass of nickel in metal ÷ (mass of all nickel in reduced product) × 100 (%) Formula (1) Nickel content in metal = mass of nickel in metal ÷ (metal Total mass of nickel and iron in the material) x 100 (%) ... (2)

The metal recovery rate was calculated from the respective amounts of the recovered metal and the metal accompanying the slag. That is, the calculation formula is as shown in formula (3).
Metal recovery rate = mass of recovered metal ÷ (mass of recovered metal + mass of metal accompanying slag) × 100 (%) ··· (3)

  Table 4 below shows the nickel metallization ratio and the nickel content of the metal in each sample.

  As can be seen from the results in Table 4, in Examples 1 to 7 in which the obtained reduced product was taken out of the reducing furnace and immediately thereafter, the reduced product was quenched, and the nickel metalization ratio and metal The content of nickel in all became high. This is considered to be because oxidation of the reduced product could be suppressed by rapidly cooling the heated reduced product immediately after being taken out of the reduction furnace.

  Further, in Examples 1 to 7, the metal recovery rate was higher than in Comparative Examples 1 to 5. This is presumably because the reduced product was quenched to cause cracks at the interface between the metal and the slag, thereby effectively separating the metal phase and the slag phase.

Claims (5)

A reduction step of charging a mixture containing an oxide ore and a carbonaceous reducing agent into a reduction furnace and performing a heat reduction treatment;
A quenching step of taking out the obtained reduced product from the reduction furnace and immediately cooling the reduced product immediately thereafter,
A separation step of separating metal and slag from the quenched reduced product, and a smelting method of an oxide ore. The smelting method of an oxide ore according to claim 1, wherein in the quenching step, the obtained reduced product is put into water and quenched. The smelting method of an oxide ore according to claim 1, wherein in the reduction step, the reduction is performed at a reduction temperature of 1200 ° C. or more and 1450 ° C. or less. The method for smelting an oxide ore according to any one of claims 1 to 3, wherein in the reduction step, after the heat reduction treatment, the obtained reduced product is kept at a predetermined temperature in the reduction furnace. The smelting method of an oxide ore according to any one of claims 1 to 4, wherein the oxide ore is a nickel oxide ore.

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